1. Field of the Invention
The present invention relates to an antivibration device designed to be provided between an engine and a vehicle body so as to mount the engine on the vehicle body while dampening vibration of the engine.
2. Description of the Related Art
As the above antivibration device, there has been known one type as disclosed, for example, in JP 2010-101375A. An antivibration device disclosed in JP 2010-101375A comprises a rubber mount body for supporting an engine to allow it to be mounted on a vehicle, while dampening vibration of the engine, a stopper bracket attached to a lower portion of the mount body, and a casing which houses the mount body to cover it from thereabove, and has an opening on a bottom side thereof. Each of longitudinally opposite ends of the stopper bracket is provided with a stopper rubber portion disposed in spaces-apart relation to a respective one of opposed sidewall portions (opposed peripheral edge portions of the bottom opening) of the casing by a given distance. The antivibration device is configured such that, when the own weight of the engine (static load) is applied thereto, respective distances between the stopper rubber portions and corresponding ones of the sidewall portions of the casing become approximately equal to each other, whereby an allowable amount of displacement of the mount body can be equally ensured in longitudinally opposite directions of the stopper bracket.
On the other hand, when a fairly large vibrational load (dynamic load) is input from the engine, for example, during vehicle running on a rough road, the mount body is largely deformed, and the sidewall portions of the casing are brought into contact with corresponding ones of the stopper rubber portions, so that it becomes possible to prevent the mount body from being further deformed.
In the above situation where the sidewall portions of the casing are brought into contact with corresponding ones of the stopper rubber portions, vibration of the engine is directly transmitted to a vehicle body. Thus, in view of suppressing vibration to be transmitted into a passenger compartment, it is desirable to ensure a gap (stopper gap) between each of the sidewall portions and a corresponding one of the stopper rubber portions as large as possible. However, in order to increase the stopper gap, it becomes necessary to increase a distance between the sidewall portions (an area of the bottom opening of the casing), which undesirably leads to an increase in size of the casing and thus an increase in size of the antivibration device. In an engine compartment where the antivibration device is provided, various units are disposed in adjacent relation to each other. Thus, the increase in size of the antivibration device is undesirable in terms of layout of the units within the engine compartment.
Moreover, in the antivibration device disclosed in JP 2010-101375A, for example, when a large load causing the mount body to be pulled in an upward-downward direction is applied thereto, the mount body is stretchably deformed in the upward-downward direction, and accordingly the sidewall portions of the casing are likely to be moved beyond or above the stopper rubber portions. If such a situation occurs, it becomes impossible to restrict the displacement of the mount body, so that the mount body is likely to be excessively deformed due to a large load momentarily applied thereto during vehicle running on a rough road, etc., which leads to breaking.